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  • Vibraciones de sonido pict
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  • Imagen de Hz
  • Sound

    1. 1. Presentation by Language Assistant – Liannette Bellido Cintrón Natural Sciences 2˚ ESO I.E.S. Francisco Rodríguez Marín– OSUNA, Seville JANUARY 2011
    2. 2. What is sound? <ul><li>Sound is made by an object that is vibrating or oscillating quickly. </li></ul><ul><li>Sound requires: </li></ul><ul><ul><li>An object that is vibrating. </li></ul></ul><ul><ul><li>A substance to carry it. </li></ul></ul><ul><ul><li>A receptor. </li></ul></ul>
    3. 3. How is sound made? <ul><li>Sound only occurs when a object vibrates or oscillates very quickly. </li></ul><ul><li>To produce sound, the object must oscillate between 20 and 20,000 times a second. To know if you could hear it, you need to know what frequency the sound has. </li></ul>
    4. 4. <ul><li>Frecuency is: </li></ul><ul><li>the scale that measures the different rates at which a body vibrates or oscillates. </li></ul><ul><li>The unit of measure ment </li></ul><ul><li>of frequency is Her tz (s -1 ). </li></ul>
    5. 5. <ul><li>You can hear a sound if the frequency is bigger than 20 Hz and smaller than 20,000 Hz. </li></ul><ul><li>Can you hear a sound that has a frecuency of 1,000 Hz? </li></ul><ul><li>YES </li></ul>
    6. 6. Sound needs a medium for propagation <ul><li>The mechanical vibrations that can be interpreted as sound are able to travel through all forms of matter: gases, liquids, solids, and plasmas . </li></ul><ul><li>Sound needs air to travel, so it cannot </li></ul><ul><li>travel through a vaccum. </li></ul>
    7. 7. If you could play the guitar in the Moon would it produce any sound? NO. Because there is no air in the Moon, and sound needs a medium of propagation.
    8. 8. <ul><li>1. Sound makes the air vibrate. </li></ul><ul><li>2. Sound is funnelled into the ear. </li></ul><ul><li>3. Sound runs by the outer ear. </li></ul><ul><li>4. The eardrum vibrates and the vibrations are made bigger by small bones. </li></ul><ul><li>5. Vibrations are turned into electrical signals by nerves in the cochlea. </li></ul><ul><li>6. Electrical signals go to the brain. </li></ul>
    9. 10. Speed of Sound <ul><li>The speed of sound depends on the medium through which the waves are passing, and is often quoted as a fundamental property of the material. </li></ul><ul><li>In general, the speed of sound is proportional to the elasticity of the medium to its density. Those physical properties and the speed of sound change with ambient conditions. </li></ul>
    10. 11. Pitch <ul><li>A measure of how high or low a sound is </li></ul><ul><li>Pitch depends on the frequency of a sound wave </li></ul><ul><li>For example, </li></ul><ul><li>Low pitch </li></ul><ul><li>Low frequency </li></ul><ul><li>Longer wavelength </li></ul><ul><li>High pitch </li></ul><ul><li>High frequency </li></ul><ul><li>Shorter wavelength </li></ul>
    11. 12. Loudness <ul><li>To create vibrations energy is used. </li></ul><ul><li>The greater amount of energy used the louder the sound. </li></ul><ul><li>The strength of the changes in air pressure made by the vibrating object determines loudness. </li></ul>
    12. 13. <ul><li>As the sound spreads out from its source, the concentration of power becomes less. </li></ul><ul><li>As the distance from the source increases the amount of power is spread over a greater area </li></ul><ul><li>For us to perceive a sound as twice as loud its intensity must be ten times greater. </li></ul><ul><li>The perceived intensity level of sound is measured in a scale using a unit called </li></ul><ul><li>the decibel (dB) 2 </li></ul>
    13. 14. The scale begins on the softest sound that a person can hear. This is called the threshold of hearing. <ul><li>The scale ends at the volume that causes pain and is therefore called the threshold of pain. </li></ul>
    14. 15. “ Timbre” (TAM-ber) or tone color <ul><li>Is the specific property of sound that enables us to determine the difference between two sounds produced by different instruments, for example, between a piano and a harp. </li></ul>
    15. 16. Reflection of sound <ul><li>When sound encounters an obstacle, the sound waves bounce off and reflect. </li></ul><ul><li>This causes the phenomenon called… </li></ul><ul><ul><li>ECHO </li></ul></ul>
    16. 17. Noise pollution <ul><li>Urban areas are the most affected by the noises emitted by cars, machinery, traffic, airplanes, etc. </li></ul><ul><li>You can avoid exposure to noise pollution by using special protection. </li></ul>Scientists recommend avoiding exposure to noise higher than 65dB. To control noise pollution, governments have adopted various alternatives. Acoustic walls